By Chris Halliday – PowerLogic.
A ‘green group’ traditionally tries to conserve and protect the environment but green group Bathurst Community Climate Action Network (BCCAN) is aiming to conserve volts – strange but true. Their project is a process called Conservation Voltage Reduction (CVR) which is about lowering the electricity supply voltage level to conserve energy and reduce demand and carbon dioxide emissions. This case study looks at lowering voltage levels at the Bathurst campus of Charles Sturt University (CSU) and the benefits gained.
The BCCAN received NSW Office of Environment & Heritage funding to implement a trial CVR project to see what the benefits to the environment were and whether the project could be rolled out across the state.
BCCAN’s project aimed to link with large electricity users who would benefit from reductions in peak demand and energy usage due to CVR, which would also benefit the environment. The project was designed to explore possible business models that community energy groups could use to access any carbon credits or energy reduction funds from CVR to fund community energy projects
Australia has had a 240V electricity supply since 1926 that was focused towards the higher end of an allowable voltage range (though I am led to believe that Western Australia was 250V at one stage). With an international rationalisation of voltage to 230V, planned in 1983 and introduced in Australia in 2000, a lowering of voltage is now possible.
Benefits in Lowering Voltage Levels
The benefits of lowering the voltage to around the nominal 230/400V are:
- Reduction in the quantity of energy used, which leads to the electricity bill being reduced;
- Reduction in the peak amount of energy used or what is generally called demand. Larger energy users not only pay for the energy used but also for the peak demand and so any reduction in peak demand will also help reduce the electricity bill for the site. Demand charges are typically half of a large customer’s electricity bill;
- Reduction in CO2 emissions (which is of particular interest to BCCAN);
- Extended life of electrical equipment;
- Reduced maintenance e.g. light globes won’t need to be changed as often.
Equipment that Save Energy from Lower Volts
Not all types of electrical equipment respond to a reduction in supply voltage with a reduction in energy usage, as shown in Figure 1 (table from the Office of Environment & Heritage’s document ‘i am your guide to voltage optimisation: is it right for you’).
Figure 1 – Effects of Voltage on Energy Consumption on Various Types of Equipment
The site for the trial project was at the Charles Sturt University campus at Bathurst. Twelve transformers were assessed for a reduction in voltage at the site and a high level assessment of electrical equipment was carried out to determine the suitability of the application of CVR.
One transformer did not have any available adjustment for lowering voltage and was discounted from the project. Another three transformers were also discounted for simplicity reasons due to energy efficiency works that were in progress. This left eight transformers that were assessed as able to have their voltage lowered. Three transformers could be lowered by 2.5%, four transformers by 5% and one transformer by 7.5%. Savings were estimated at $10,000/year and CO2 savings at 61tonnes/year.
Green Credit Options
The National Emissions Reduction Fund was initially considered as a source of funding but the anticipated savings were too small for the project to be eligible. Energy Savings Certificates issued under the NSW Energy Savings Scheme were then considered. Unfortunately, by this time the project had commenced with no nomination form signed with an Accredited Certificate Provider and so the project had not been accredited and no Energy Savings Certificates could be issued. Variations in the load from month to month and the lack of correlation with independent variables made determination of accurate energy savings and Energy Savings Certificates difficult.
Voltage Adjustment Mechanism
The different ways to lower voltage levels to achieve a reduction in voltage to electrical equipment are:
- Using Conservation Voltage Reduction (CVR):
- Adjust the voltage regulation relay settings at zone substation transformers and/or at voltage regulators in the field;
- Rotate the tap changer knob on the transformer (with the power off) to adjust the transformer winding (refer Figure 2), which is the low cost option chosen for this project;
- Installing a voltage optimiser at the electrical installation. Voltage optimisers are series devices and so all the load current flows through them and they adjust the voltage output. These provide typical savings of up to 12% but cost more;
- The ability to lower voltage will depend on the available adjustment of transformers and the existing voltage levels.
Voltage Optimisers versus Conservation Voltage Reduction
Voltage optimisers are likely to produce greater energy and demand savings than CVR as the voltage output is generally regulated to a near constant value but this does depend on the type of optimiser (refer to the table below). Voltage optimisers and CVR have various positives and negatives – these are explored in Figure 3.
Figure 3 – Voltage Optimiser versus Conservation Voltage Reduction
Results of Trial
Voltage levels lowered as expected with the graph in Figure 3 showing the voltage levels before the transformer tap was dropped by 5% and the voltage levels after the change.
Figure 3 – Voltage Levels Before and After the Tap Change at One Substation
Raw energy savings were better than expected and calculated at 94,970kWh and $7,760 for the six-month period from February to July 2016 but these figures hold no statistical relevance or accuracy due to the lack of correlation with independent variables.
Demand savings were also better than expected and were estimated at $2,220 for the three-month period from February to April 2016. A different time period was used due to data collection issues.
Further detail on the raw energy and demand savings is contained within our full report.
CO2 savings could not be accurately calculated due to lack of correlation with independent variables.
CVR can result in significant energy, demand and maintenance savings and generate worthwhile numbers of Energy Saving Certificates but this is all dependent on the size of the installation, the type of installed electrical equipment, correlation with independent variables and the existing voltage levels. The cost of CVR is minimal when compared with voltage optimisers and in fact some voltage optimisers only do what CVR performs.
Linking with a voltage consultant and an Accredited Certificate Provider in the early stages of the project is essential. Using the flowchart provided in the full report will help to ensure the success of any CVR project.
The real question is whether this type of project is viable for a community group such as BCCAN and large electricity users such as CSU to link together? Community groups will need to find large energy users that are willing to work with them, while skilled voltage and energy consultants will be necessary to prevent problems. The lack of measuring equipment and the cost of the consultants are likely to take any Energy Savings Certificate revenue that might be generated and the community group might be out of pocket if the energy savings are less than expected.
CVR does however provide a real opportunity for distribution network businesses to reduce greenhouse gas emissions but they are unlikely to be eligible for any Energy Saving Certificates. There are also no other incentives for them to reduce their customer’s energy usage and their resulting income. It would take government intervention for network businesses to lower their voltage levels and this should occur if we as a country are serious about reducing greenhouse gases. A whole system level lowering of voltage levels would reduce any business opportunity for community energy groups to negotiate further reductions in voltage at a local level.